linux-kernel - Re: [PATCH v5 1/2] dt-bindings: iio: vadc: Update example to include unit address for node 'usb-id-nopull'

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Date:   Thu, 11 Oct 2018 13:52:58 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Rob Herring <robh@...nel.org>
Cc:     Andy Gross <andy.gross@...aro.org>,
        David Brown <david.brown@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        Jonathan Cameron <jic23@...nel.org>,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        linux-arm-msm@...r.kernel.org, linux-soc@...r.kernel.org,
        devicetree@...r.kernel.org, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Douglas Anderson <dianders@...omium.org>
Subject: Re: [PATCH v5 1/2] dt-bindings: iio: vadc: Update example to include
 unit address for node 'usb-id-nopull'

On Thu, Oct 11, 2018 at 12:11:34PM -0700, Matthias Kaehlcke wrote:
> Hi Rob,
> 
> On Fri, Oct 05, 2018 at 03:47:43PM -0500, Rob Herring wrote:
> > On Wed, Oct 03, 2018 at 05:14:31PM -0700, Matthias Kaehlcke wrote:
> > > The node has a reg property, therefore its name should include a unit
> > > address.
> > > 
> > > Also change the name from 'usb_id_nopull' to 'usb-id-nopull' to follow
> > > DT conventions.
> > 
> > This is ADC channels?
> 
> yes
> 
> > If so, then DT convention would really be "adc@...". 
> 
> ok, will update
> 
> > > Signed-off-by: Matthias Kaehlcke <mka@...omium.org>
> > > ---
> > > Changes in v4:
> > > - patch added to the series
> > > ---
> > >  Documentation/devicetree/bindings/iio/adc/qcom,spmi-vadc.txt | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/Documentation/devicetree/bindings/iio/adc/qcom,spmi-vadc.txt b/Documentation/devicetree/bindings/iio/adc/qcom,spmi-vadc.txt
> > > index d0c188e5c922..ff7aa5038ba6 100644
> > > --- a/Documentation/devicetree/bindings/iio/adc/qcom,spmi-vadc.txt
> > > +++ b/Documentation/devicetree/bindings/iio/adc/qcom,spmi-vadc.txt
> > > @@ -112,7 +112,7 @@ Example:
> > >  		io-channel-ranges;
> > >  
> > >  		/* Channel node */
> > > -		usb_id_nopull {
> > > +		usb-id-nopull@...C_LR_MUX10_USB_ID {
> > >  			reg = <VADC_LR_MUX10_USB_ID>;
> > 
> > Defines are generally used when there's not well defined numbering such 
> > as clock ids. Interrupts and addresses are generally well defined and 
> > don't need defines.
> 
> ok, I'll update this to use literals

Actually I'm not convinced literals are the right answer here. It
makes perfect sense for a standard ADC, with a 1:1 mapping of channel
number and physical input. However in case of the VADC/ADC5 there
can be multiple channel numbers per input pin, the different values
are used to select a certain 'configuration' (eg. ADC5_BAT_THERM,
ADC5_BAT_THERM_30K_PU, ADC5_BAT_THERM_100K_PU,
ADC5_BAT_THERM_400K_PU). IMO using integer channel numbers here would
be more error prone and obfuscating than using the defines.